Abstract

We report an updated measurement of the CP-violating phase, $\phi_s^{J/\psi \phi}$, and the decay-width difference for the two mass eigenstates, $\Delta \Gamma_s$, from the flavor-tagged decay $B_s^0 \rightarrow J/\psi \phi$. The data sample corresponds to an integrated luminosity of 8.0 fb$^{-1}$ accumulated with the D0 detector using $p \barp$ collisions at $\sqrt{s} = 1.96$ TeV produced at the Fermilab Tevatron collider. The 68% confidence level intervals, including systematic uncertainties, are $\Delta \Gamma_s = 0.163 +0.065 -0.064 ps^{-1}$ and $\phi_s^{J/\psi \phi} = -0.55 +0.38 -0.36$. The $p$-value for the Standard Model point is 29.8%.